page_title: Sigma Scorpii
section_title: Nomenclature
hierarchical_section_title: Sigma Scorpii / Nomenclature
caption_attribution_description: English: A rich collection of colourful astronomical objects is revealed in this picturesque image of the Rho Ophiuchi cloud complex from NASA’s Wide-field Infrared Explorer, or WISE. The Rho Ophiuchi cloud (pronounced ‘oh-fee-yoo-ki’ and named after a bright star in the region) is found rising above the plane of the Milky Way in the night sky, bordering the constellations Ophiuchus and Scorpius. It’s one of the nearest star-forming regions to Earth, allowing us to resolve much more detail than in more distant similar regions, like the Orion nebula. The amazing variety of different colours seen in this image represents different wavelengths of infrared light. The bright white nebula in the centre of the image is glowing due to heating from nearby stars, resulting in what is called an emission nebula. The same is true for most of the multi-hued gas prevalent throughout the entire image, including the bluish bow-shaped feature near the bottom right. The bright red area in the bottom right is light from the star in the centre – Sigma Scorpii – that is reflected off of the dust surrounding it, creating what is called a reflection nebula. And the much darker areas scattered throughout the image are pockets of cool dense gas that block out the background light, resulting in absorption (or ‘dark’) nebulae. WISE’s longer wavelength detectors can typically see through dark nebulae, but these are exceptionally opaque. The bright pink objects just left of centre are young stellar objects (YSOs). These baby stars are just now forming; many of them are still enveloped in their own tiny compact nebulae. In visible light, these YSOs are completely hidden in the dark nebula that surrounds them, which is sometimes referred to as their baby blanket. We can also see some of the oldest stars in our Milky Way Galaxy in this image, found in two separate (and much more distant) globular clusters. The first cluster, M80, is on the far right edge of the image towards the top. The second, NGC 6144, is found close to the bottom edge near the centre. They both appear as small densely compacted groups of blue stars. Globular clusters such as these typically harbour some of the oldest stars known, some as old as 13 billion years, born soon after the Universe formed. There are two other items of interest in this image as well. At the 3 o’clock position, relative to the bright central region, and about two-thirds of the way from the centre to the edge, there is a small faint red dot. That dot is an entire galaxy far, far away known as PGC 090239. And, at the bottom left of the image, there are two lines emerging from the edge. These were not created by foreground satellites; they are diffraction spikes (optical artefacts from the space telescope) from the bright star Antares that is just out of the field of view.
context_page_description: Sigma Scorpii, is a multiple star system in the constellation of Scorpius, located near the red supergiant Antares, which outshines it. This system has a combined apparent visual magnitude of +2.88, making it one of the brighter members of the constellation. Based upon parallax measurements made during the Hipparcos mission, the distance to Sigma Scorpii is roughly 696 light-years. North et al. computed a more accurate estimate of 568+75
  −59 light years.
  The system consists of a spectroscopic binary with components designated Sigma Scorpii Aa1 and a Beta Cephei variable and Aa2; a third component at 0.4 arcseconds from the spectroscopic pair, and a fourth component at about 20 arcseconds.
context_section_description: σ Scorpii (Latinised to Sigma Scorpii) is the star system's Bayer designation. The designations of the four components as Sigma Scorpii Aa1, Aa2, Ab and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
  Sigma Scorpii and Tau Scorpii together bore the traditional name Al Niyat (or Alniyat) derived from the Arabic النياط al-niyāţ "the arteries" and referring to their position flanking the star Antares, the scorpion's heart, with Sigma Scorpii just to the north. 
  In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name Alniyat for the component Sigma Scorpii Aa1 on February 1, 2017 and it is now so included in the List of IAU-approved Star Names.
  In Chinese, 心宿 (Xīn Xiù), meaning Heart, refers to an asterism consisting of Sigma Scorpii, Antares and Tau Scorpii. Consequently, the Chinese name for Sigma Scorpii itself is 心宿一 (Xīn Xiù yī), "the First Star of Heart".
  The indigenous Boorong people of northwestern Victoria in Australia saw this star and Tau Scorpii as wives of Djuit (Antares).
caption: The red at bottom right is light from Sigma Scorpii being reflected off the surrounding dust.
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